1. Field of the Invention
The present invention relates to a method of creating an analysis model and to a program for creating an analysis model.
2. Description of the Related Art
Design works involve numerical analysis simulation of designed products and review of the design content on the basis of the analysis results. In such an analysis, the numerical analysis simulation is performed to several patterns resulting from modification of a basic shape to confirm the analysis results of each pattern.
For example, strength analysis or vibration analysis of an assembly will now be considered. FIG. 20 is a schematic perspective view illustrating an exemplary assembly designed by a designer. The assembly in FIG. 20 has a structure in which a part 200 having a mounting hole 201 is joined to a part 202 having a mounting hole 203 via the mounting holes with a connecting part (not shown), such as a screw. The designer performs desired analysis to the assembly with the mounting holes 201 and 203 bored in the tabular parts 200 and 202, respectively.
FIG. 21 is another schematic perspective view of the assembly shown in FIG. 20, in which a rib 216 is provided on the surface of the part 200. The rib 216 does not concern the connection between the part 200 and the part 202. The assembly in FIG. 21 results from design change in which the mounting holes 201 and 203 are shifted in a direction denoted by an arrow 212 to mounting holes 214 and 215, respectively. The designer performs the analysis again after the design change to confirm a change in the stress state or vibration state caused by the shift of the holes in which the screw is mounted and the addition of the rib 216.
Methods in related art are proposed to create an analysis model from a shape model of an assembly. In a first method, an apparatus searches the shape model of the assembly for the shape features of connecting parts. Then, an operator selects a candidate for the connection type of each shape feature that has been searched for. The apparatus automatically creates a finite element model (FEM) of the connecting part of the selected connection type on the basis of a creating process stored in a database (for example, refer to Japanese Patent Laid-Open No. 2003-337836).
In a second method, after mesh data about each part is generated in advance and layout of the parts is performed, an analysis model is newly added to each joint part between the parts to automatically recreate the analysis models of the parts that are shifted to other positions (for example, refer to Japanese Patent Laid-Open No. 2005-250647).
However, the method of creating an analysis model and the apparatus of creating an analysis model in the related art have the following problems. When the assembly in FIG. 20 is subjected to the design change to provide the assembly in FIG. 21, it is necessary to create the analysis model for each designed assembly to perform the analysis. During the development and analysis, the shapes of products are frequently changed not only to perform the strength or vibration analysis but also to meet restrictions on other parts. Accordingly, the analysis models are recreated and reviewed in response to the shape change.
It takes a very long time to create an analysis model from the shape model of an assembly produced by a computer aided design (CAD) system in the related art. In particular, much effort is expended to model the connecting parts between the parts. In addition, if even part of the shape model is modified, it is necessary to recreate an analysis model from the first on the basis of the modified shape model or to modify the created analysis model so as to support the change in the shape model.
The former operation means full recreation of the analysis models and much effort is expended because the analysis model before the modification is discarded and a new analysis model is recreated from the first. In the latter operation, the shape of the mesh of the created analysis model is directly edited. However, it is not easy and much effort is expended to edit the analysis model. Accordingly, the use of the previous analysis model does not have a big advantage.
A technology called morphing is adopted to effectively use an analysis model that is created. In the morphing, the mesh is modified while keeping the relationship between adjacent parts. However, it is difficult to precisely control the mesh shape of certain parts, such as the connecting parts, and certain functional parts and editing of the mesh by an engineer is essential to coincidence between the analysis results and the actual phenomena.
Specifically, with the first method, it is difficult to automatically search the shape model for the shape features of connecting parts and create the analysis models of the connecting parts from the shape model. Accordingly, it takes a very long time for an operator to search for and select the shape features and to select and instruct a process of creating an analysis model. Also if part of the shape is modified, it takes a very long time because it is necessary for the operator to perform the above operations again.
With the second method, it is necessary to rebuild the mesh shape of each part around a connecting part in accordance with the arrangement of the parts even if the mesh shape of each part composing an assembly is set in advance. In this process, it is difficult to automate recognition of the connecting part in accordance with the arrangement of the parts, selection of an appropriate process of creating an analysis model of the connecting part, and matching between the set mesh shape of each part and the rebuilt mesh shape of each part around the connecting part. Accordingly, when the arrangement of the parts is changed, it takes a very long time because it is necessary for an operator to perform the above operations.